As one of the causes of global warming, the greenhouse effect by CO2 has been identified, and a countermeasure thereof is urgently required internationally from the viewpoint of protecting the global environment. Sources of CO2 emission spread over various fields of human activity where fossil fuel is burned, and demand on emission reduction of CO2 tends to increase. As a result, for power generation facilities such as a thermal power plant where a large amount of fossil fuel is used, a CO2 recovery method has been actively studied in which flue gas of a boiler is brought into contact with an amine-based absorption solution such as an aqueous amine compound solution so as to remove and recover CO2 from the flue gas.
When CO2 is recovered from flue gas using such an absorption solution, decarbonated flue gas from which CO2 has been recovered is accompanied by amine compounds. In order to prevent air pollution by the amine compound, it is necessary to reduce the amount of the amine compound emitted along with the decarbonated flue gas.
In the related art, PTL 1 discloses an amine recovery process in which the amine compound accompanying decarbonated flue gas, from which CO2 has been absorbed and removed by gas-liquid contact with an absorption solution, is sequentially recovered in plural stages of water-washing sections that are provided for bringing the decarbonated flue gas into gas-liquid contact with washing water to recover the amine compound. As the washing water disclosed in PTL 1, condensate is used, the condensate being obtained by condensing and separating moisture contained in CO2 in a treatment in which CO2 is removed from the CO2-absorbed amine-based absorption solution to regenerate the amine-based absorption solution.
In addition, in the related art, PTL 2 discloses a configuration in which the washing efficiency is further improved by providing plural stages of water-washing sections and washing the decarbonated flue gas with acidic water in an uppermost water-washing section among the plural stages of water-washing sections.